Tools for customized design of dental restorations

ABSTRACT

The present invention relates to tools in a system for the design of customized three-dimensional models of dental restorations for subsequent manufacturing. Dental restorations such as implant abutments, copings, crowns, wax-ups, bridge frameworks. Moreover, the invention relates to a computer-readable medium for implementing such a system on a computer.

The present invention relates to tools in a system for the design ofcustomized three-dimensional models of dental restorations forsubsequent manufacturing. Dental restorations such as implant abutments,copings, crowns, wax-ups, bridge frameworks. Moreover, the inventionrelates to a computer-readable medium for implementing such a system ona computer.

BACKGROUND OF INVENTION

The present invention is related to the field of designing andmanufacturing of dental restorations such as crowns, bridges, copings,abutments and implants. When a patient requires a dental restoration thedentist will prepare the teeth e.g. a damaged tooth is grinded down tomake a preparation where the crown is glued onto. An alternativetreatment is to insert implants (titanium screws) into the jaw of thepatient and mount crowns or bridges on the implants.

CAD technology for manufacturing dental restorations is rapidlyexpanding resulting in improved quality, reduced cost and facilitationof the possibility to manufacture in attractive materials otherwise notavailable. The first step in the CAD manufacturing process is to createa 3-dimensional dental model of the patient's teeth. This is provided by3D scanning of one or both of the dental gypsum models or by scanningimpressions of the teeth. The 3-dimensional replicas of the teeth areimported into a CAD program, where the entire dental restoration or abridge substructure is designed. The final restoration 3D design is thenmanufactured e.g. using a milling machine, 3D printer, rapid prototypingmanufacturing or other manufacturing equipment. Accuracy requirementsfor the dental restorations are very high otherwise the dentalrestoration will not be visual appealing, fit onto the teeth, couldcause pain or cause infections.

Systems for designing dental restorations are known in the art, e.g.3Shape DentalDesigner™ and 3Shape AbutmentDesigner™, which are generallyused by dental specialists such as dental technicians. Users of suchdesign tool systems are working with a three dimensional dental model ofthe patient trying to fit the dental restoration model into the dentalmodel. During dental restoration of a patients teeth the typicalprocedure could be to secure an implant abutment in the jaw of thepatient, a coping is then attached (e.g. by glue) to the abutment andfinally a crown is glued onto the coping. However, both abutment, copingand crown must be designed to fit the patient, both physically andvisually. I.e. the abutment, the coping and the crown must be customizedfor each tooth of each patient.

In the following the term “dental restoration” can be an implantabutment, a coping, a crown or any combination of these. Correspondinglya “dental restoration model” can be an abutment model, a coping model, acrown model or any combination of these.

In the design phase of a dental restoration a three dimensional model ofthe dental restoration is typically provided by the system and the taskof the dental specialist is to shape the dental restoration model toprovide a perfect fit in the dental model, whereby the patient can endup with a tooth implant that matches the other teeth of the patient. Adental specialist (i.e. a user of the system) is typically working witha dental model with at least one attached dental restoration model on ascreen and the 3D models can typically be rotated around any axis,zoomed, panned and the like. Thus the user will typically be able tospecify and change the orientation and viewing angle of the dental modeland the dental restoration model. The task of a user is to shape andcustomize the dental restoration model into the dental model bytranslating, rotating, dragging, tilting, widening and/or narrowing the3D dental restoration model (which preferably is fixed in the dentalmodel). This is typically provided by use of an electronic screenpointing tool, such as a mouse, a ball pen or the like. In the followingany reference to a “mouse cursor” or a “mouse marker” is a reference tothe element on the screen representing the electronic screen pointingtool.

The dental restoration model can be customizably shaped by means of thepointing tool by shaping (“dragging”) the dental restoration model withorigin in specific points on the dental restoration model. These pointsare in the following termed “control points” and can be seen in FIG. 1.The control points are typically located in carefully and preferablyautomatically selected positions on the dental restoration model. Forexample in FIG. 1 showing an abutment model where the control points arelocated on the top center, each of the four sides and around the lowerbottom rim (i.e. the lower collar of the abutment).

SUMMARY OF INVENTION

When creating a dental restoration model certain rules must be applied,for example in terms of distance to adjacent teeth and gingival ridgeand integration into the gingival. Measuring and checking thesedistances can be a cumbersome process during the design and creation ofa dental restoration model, thus an object of the invention is toprovide an intuitive and quick indication of distances betweenneighbouring and adjacent objects in the process of creating a customdental restoration.

This is achieved by a system for designing at least one dentalrestoration, said system having a display, such as a computer screen,and comprising:

-   -   means for acquiring and displaying a three dimensional model of        the dental restoration and/or a three dimensional dental model        wherein the dental restoration must be fitted,    -   means for displaying a plurality of control points at the three        dimensional model of the dental restoration, the control points        preferably located at the edges of the dental restoration model        and each of said control points providing means for manually        customizing the dental restoration model.

The invention further relates to method for designing at least onedental restoration at a display, a display such as a computer screen,said method comprising the steps of:

-   -   acquiring and displaying a three dimensional model of the dental        restoration and/or a three dimensional dental model wherein the        dental restoration must be fitted,    -   displaying a plurality of control points at the three        dimensional model of the dental restoration, the control points        preferably located at the edges of the dental restoration model        and each of said control points providing means for manually        customizing the dental restoration model.

In a further embodiment of the invention means for displaying an arrowat least one of the control points is provided. The length of said arrowis preferably determined by a user defined value, whereby the distancebetween the dental restoration model and neighbouring objects can bemeasured or indicated.

Thus, for a dental specialist in the process of creating a dentalrestoration this invention provides a quick real-time distance indicatorwhen shaping the dental restoration model. For example when the dentalspecialist is varying the width of the dental restoration model bydragging the model in a control point, an arrow with origin in thespecific control point will, by the length of said arrow, indicate acertain distance from the dental restoration model. The length of thearrow is determined by the user (i.e. the dental specialist in thiscase), thus if the user in advance knows that the distance from thedental restoration to the neighbouring tooth should be 1.5 mm, thelength of the arrow is specified to 1.5 mm and when widening the dentalrestoration model by dragging a control point, the arrow with origin insaid control point will indicate for the user when the distance to theneighbouring tooth is 1.5 mm. Thus, adjusting a dental restoration modelto the correct width can be provided within seconds by the system andmethod according to the invention.

In a further embodiment of the invention means for displaying a grid atleast one control point is comprised. The size of the grid is determinedby a user defined value. This grid provides the user with yet anotherway of measuring the distance to adjacent objects. The grid can have theappearance of a square divided into smaller and preferably equally sizedsquares, for example the grid can be a square of height and width of 1mm divided into 4 squares of height and width 0.5 mm, or 16 squares ofheight and width 0.25 mm. An example of a grid can be seen in FIG. 7.Unlike an arrow a grid can provide an indication of a distance betweentwo unaligned points, i.e. the grid can provide the orthographicprojection distance between two points.

A second embodiment of the invention relates to a system for designingat least one dental restoration, said system having a display, such as acomputer screen, and comprising:

-   -   means for acquiring and displaying a three dimensional model of        the dental restoration and/or a three dimensional dental model        wherein the dental restoration must be fitted, and    -   means for displaying an arrow adjacent to the edge of the dental        restoration model, the length of said arrow determined by a user        defined value, whereby the distance between the dental        restoration model and neighbouring objects can be measured or        indicated, and/or    -   means for displaying a grid adjacent to the edge of the dental        restoration model, the size of said grid determined by a user        defined value, whereby the distance between the dental        restoration model and neighbouring objects can be measured or        indicated.

Correspondingly the invention relates to a method for designing at leastone dental restoration at a display, a display such as a computerscreen, said method comprising the steps of:

-   -   acquiring and displaying a three dimensional model of the dental        restoration and/or a three dimensional dental model wherein the        dental restoration must be fitted, and    -   displaying an arrow adjacent to the dental restoration model,        the length of said arrow determined by a user defined value,        whereby the distance between the dental restoration model and        neighbouring objects can be measured or indicated, and/or    -   displaying a grid adjacent to the dental restoration model, the        size of said grid determined by a user defined value, whereby        the distance to neighbouring objects can be indicated.

Preferably the arrow and/or the grid is located at the edge of thedental restoration model, preferably pointing towards a neighbouringobject. Naturally the arrow and/or the grid may also be displayedadjacent to, preferably at the edge of, a neighbouring object (such asthe dental model).

DETAILED DESCRIPTION OF THE INVENTION

If each control point of the dental restoration model is showing anarrow or a grid, a confusing picture will be provided to the user. Thusin a preferred embodiment of the invention an arrow or a grid of acontrol point is only displayed under certain circumstances, preferablywhen the control point is activated. In a preferred embodimentactivation of a control point is provided when the mouse cursor is closeto a control point. “Close to” in the meaning of within a certain numberof pixels on the screen and/or within a certain distance from thecontrol point. Thus, an arrow or a grid of a control point is preferablyonly visible when the mouse marker is close to said control point. Inanother embodiment of the invention an arrow or a grid is only visiblewhen the mouse marker is close to the origin of said arrow or grid.

In specific embodiments of the invention an arrow or grid is onlyvisible when the mouse cursor is within a distance of preferably 10pixels from a corresponding control point and/or the origin of saidarrow or grid, such as within a distance of 100 pixels, such as within adistance of 80 pixels, such as within a distance of 60 pixels, such aswithin a distance of 40 pixels, such as within a distance of 30 pixels,such as within a distance of 20 pixels, such as within a distance of 15pixels, such as within a distance of 12 pixels, such as within adistance of 8 pixels, such as within a distance of 6 pixels, such aswithin a distance of 5 pixels, such as within a distance of 4 pixels,such as within a distance of 3 pixels, such as within a distance of 2pixels, such as within a distance of 1 pixel from a correspondingcontrol point and/or the origin of said arrow or grid.

The length of an arrow or the size of a grid can be defined by the user,e.g. by a graphical menu. However, means for varying the length of anarrow or the size of a grid can advantageously be provided to the usersimultaneous with an activation of a control point. Thus, in a preferredembodiment of the system the length of an arrow or the size of a gridcan be adjusted when a control point is activated. This adjustment canpreferably be provided by means of user interaction, such as a screenpointing tool action, e.g. by turning the scroll wheel of the mouse. Inthis case a specific revolution of the scroll wheel is transferred to aspecific increase or decrease of the length of the arrow or the size ofthe grid. For example a revolution of 5 degrees of the scroll wheelcould correspond to a change in 0.1 mm in the length of an arrow or thesize of a grid.

Correspondingly for other types of screen pointing tools with or withoutvariable buttons, scroll wheels and/or the equivalents of that. Forpractical reasons the numerical value of the length of the arrow or thesize of the grid may be displayed to the user on the screen concurrentlywith the user interaction, e.g. the user can see the numerical value ofthe length of an arrow while turning the scroll wheel of the mouse.

When customizing the dental restoration model in a dental model it mightbe necessary to both expand, tilt and rotate the dental restorationmodel. A solution where each control point has only one functionality(e.g. the functionality of “rotation”) requires a great number ofcontrol points on the dental restoration model, possibly creating aconfusing Graphical User Interface (GUI) for the user. In a preferredembodiment of the invention the functionality of at least one controlpoint is variable, i.e. at least one of the control points has more thanone function and the user can shift between these functions. Shiftingthe functionality of a control point can be provided in numerous ways inthe GUI (e.g. by means of menus, buttons and/or the like). However, forthe user a quick shift in functionality is advantageous, preferablywithout moving the mouse away from the control point, i.e. the user canpreferably change the functionality of a control point when said controlpoint is activated. For practical reasons the specific functionality ofa control point can be indicated by a symbol on the screen to ease theuser interaction. E.g. a specific symbol near a control pointcorresponds to a specific current functionality of the control point.Examples of functionality symbols are illustrated in FIG. 14.

Furthermore, the functionality of a control point can preferably bechanged by some specific activation of the mouse. A known specificactivation is the “double-click” of a mouse button. Another specificactivation is a “quick click” on a mouse button. By a “quick click” isunderstood a click on a mouse button executed within a certain timeinterval, for example with 0.5 seconds. I.e. the mouse button isactivated in a time period less than the specified time interval. If theclick execution is slower (i.e. the mouse button is activated in a timeperiod longer than the specified time interval) nothing will happen. Thetime interval may be predefined and/or may be specified by a user. This“quick click” feature greatly enhances the dental restoration modellingexperience for the user. Within seconds the dental restoration model canbe dragged, widened, tilted and/or rotated by just few clicks on themouse.

However, not all possible functionalities of a control point are alwaysrelevant. For example when the dental model and the dental restorationmodel are seen from the side. In this case a rotation of the dentalrestoration around the long axis is irrelevant to the user. And when adental restoration model is seen from the top a variation of the heightof the dental restoration is also irrelevant for the user. Thus, in apreferred embodiment of the invention the functionality of at least onecontrol point is depending on the orientation of the dental restorationmodel. I.e. orientation in the meaning of the view angle of the dentalrestoration model seen by the user.

The orientation of the dental model and the dental restoration model isalso relevant in other circumstances. The user will typically shape thedental restoration model when viewed along with the dental model.However, because the dental restoration is typically located betweenadjacent teeth the dental model can block the view of the dentalrestoration model for the user for certain view angles. Thus, thedisplay of at least a part of the dental model is preferably dependingof the orientation of the dental model, i.e. the view angle for theuser. This dental restoration view blocking can preferably be solved byletting at least part of the dental model be invisible for certainorientations, preferably the invisible part of the dental model is thepart that is between the user and the dental restoration model. Therebythe dental restoration model can be seen by the user for any orientationof the dental model.

In one embodiment of the invention the control points of the dentalrestoration model are a central part of the system. However, theappearance of all the control points can disturb the image of the dentalrestoration model when trying to create the perfect fit into the dentalmodel. In a preferred embodiment of the invention the control points areonly visible when the mouse marker (cursor) is within a specificdistance from the dental restoration model. This specific distance canbe a specific number of pixels on the screen or a specific distancerelated to the dental model and the dental restoration model. The dentalmodel is a replica of a patient's teeth, thus the specific dimensions ofthe dental model are known exactly and at least one coordinate system isembedded in the system according to the invention. Thus, it can bespecified in the system that the control points are only visible whenthe mouse marker is within a distance of a specific number ofmillimetres.

In specific embodiments of the invention the control points are onlyvisible when the mouse cursor is within a distance of preferably 10pixels from the dental restoration model, such as within a distance of500 pixels, such as within a distance of 300 pixels, such as within adistance of 200 pixels, such as within a distance of 100 pixels, such aswithin a distance of 80 pixels, such as within a distance of 60 pixels,such as within a distance of 40 pixels, such as within a distance of 30pixels, such as within a distance of 20 pixels, such as within adistance of 15 pixels, such as within a distance of 12 pixels, such aswithin a distance of 8 pixels, such as within a distance of 6 pixels,such as within a distance of 5 pixels, such as within a distance of 4pixels, such as within a distance of 3 pixels, such as within a distanceof 2 pixels, such as within a distance of 1 pixel from the dentalrestoration model.

A situation where the user is working on at least two dental restorationmodels in the same dental model can occur. This can for example be thecase when two adjacent abutments are being designed. In this case theappearance of control points in both dental restoration models canconfuse the image for the user. This can preferably be overcome by onlyshowing the control points on the dental restoration model closest tothe mouse marker.

A significant part of a dental restoration may be located below thegingival, especially when the dental restoration mode is an abutmentmodel. Thus, when customizing a dental restoration model in a dentalmodel, a part of the dental restoration model is hidden by the gingivalof the dental model. It was previously indicated that if the dentalmodel is blocking the view of the dental restoration model the blockingpart of the dental model would advantageously become invisible to theuser. However this is not a good solution in all cases, because if thedental model was invisible when trying to shape the dental restorationmodel to fit into the gingival of dental model, a perfect fit would bealmost impossible. This can be solved by changing the transparency ofthe dental model. Thus, in a preferred embodiment of the invention thetransparency of the dental model is variable. The transparency of thedental model is preferably automatically adjusted when needed, forexample when the mouse cursor is close to a control point below thesurface of the dental model. This is very helpful to the user, becausethe entire dental restoration model and the control points are therebyvisible and the dental restoration model can be shaped to fit a dentalmodel that is still visible but transparent. The transparency can forexample be adjusted to 50%, where 0% transparency is the normal image,i.e. see through is impossible, and 100% transparency is totallyinvisible.

The systems and methods according to the invention furthermore regardthe embodiments wherein the dental restoration is an implant abutment, acoping, a crown and/or any combination of these. Correspondingly, theinvention regards the embodiments wherein a dental restoration model isan abutment model, a coping model, a crown model or any combination ofthese.

The invention furthermore includes a computer program product having acomputer readable medium, said computer program product comprising meansfor carrying out any of the listed methods.

DESCRIPTION OF DRAWINGS

The invention will now be explained in greater details with reference tothe figures showing embodiments of the invention where the dentalrestoration is one or more abutments.

FIG. 1 shows a 3D model of a dental restoration model, in this case animplant abutment with 6 control points, the mouse marker is close to theabutment,

FIG. 2 shows a 3D model of the abutment in FIG. 1, but the controlpoints are hidden because the mouse marker is not near the abutment,

FIG. 3 shows two abutments with control points on only the left abutmentwhere the mouse marker is located,

FIG. 4 shows an abutment surrounded and partly hidden by a dental model,

FIG. 5 shows the abutment in FIG. 4; when the mouse marker is close tothe abutment the dental model becomes transparent whereby control pointsbeneath the surface of the dental model become visible,

FIG. 6 shows an arrow in one of the control points, the arrow having auser defined length indicating the distance between an implant abutmentand the adjacent tooth in the surrounding dental model,

FIGS. 7 & 8 shows a grid in a control point, the grid having userdefined partitions into squares indicating the distance between animplant abutment and the adjacent tooth (FIG. 7) and the gingival ridge(FIG. 8) respectively,

FIG. 9 shows an abutment and the surrounding dental model,

FIG. 10 is a rotated view of FIG. 9 where the part of the dental modelobstructing a user the view of the abutment is invisible,

FIG. 11 shows an abutment surrounded by a dental model and a grid at oneof the lower control points with a translational functionality, and

FIG. 12 shows the abutment in FIG. 13 rotated to a top view where thecontrol point, that in FIG. 13 was a translational control point anddisplaying a grid when activated, has now changed functionality tobecome a rotational control point because of the changed point of view.

FIG. 13 shows a close up of a control point in FIG. 12,

FIG. 14 shows four views of the same abutment being customized, thecontrol points in the top part shift functionality, and

FIG. 15 is a screen shot of one embodiment of the system according tothe invention.

DETAILED DESCRIPTION OF THE DRAWINGS

A 3D model of an implant abutment is shown in FIGS. 1 and 2. When thefinished abutment is inserted into the mouth of the patient, thethreaded part 5 of the abutment goes into the jaw of the patient withthe collar 6 just below the gingival. A crown is glued onto theabutment. In FIG. 2 the sides 7, 7′ and the top part 8 of the abutmentis indicated. In FIG. 1 an abutment model corresponding to the abutmentmodel in FIG. 2 is shown along with a plurality of control points, 2,2′, 2″, 3, 3′, 4. The control points are located along the edges of theabutment model, i.e. round the collar 2, 2′, 2″, at the sides 3, 3′ andat the top 4 of the abutment model. The control points are visiblebecause the mouse cursor 1 is near the abutment model. In most of thefigures the mouse cursor 1 is represented by a white arrow pointing upand left.

FIG. 3 shows two adjacent abutment models, however control points areonly visible at the left abutment model because the mouse cursor 1 islocated at said left abutment model.

FIG. 4 shows an abutment model surrounded by a dental model wherein theabutment model must be fitted. The mouse cursor 1 is in the bottom leftcorner of FIG. 4. Part of the abutment model is hidden below the dentalmodel, e.g. the collar of the abutment model is invisible. FIG. 5 showsthe abutment and dental model of FIG. 4 when the mouse cursor 1 is nearthe abutment model. The control points are now visible, also the threecontrol points 2, 2′, 2″ round the collar of the abutment model, and thetransparency of the dental model has changed whereby the previouslyhidden parts of the abutment model is now visible through the dentalmodel.

FIG. 6 shows an abutment model surrounded by a dental model with visiblecontrol points. The mouse cursor is very close to one of the controlpoints along the left side of the abutment, whereby an arrow 9 isvisible. The length of the arrow 9 can be defined by the user, thelength defined as the length from the origin to the tip of the arrow,the origin being the edge of the abutment model at the control point.The arrow 9 can thereby indicate a distance from the abutment to anobject. In FIG. 6 the arrow 9 is indicating the distance from theabutment to the adjacent tooth 11. Thus when customizing the abutmentmodel, e.g. widening the abutment model by dragging the model in acontrol point, the arrow 9 can in real-time (i.e. concurrently withdragging the model) indicate the distance to the neighbouring tooth.

FIG. 7 shows a close up of an abutment model in a partly transparentdental model. The mouse cursor is close to a control point at the collarof the abutment model thereby initiating the display of the grid 10. Thesize of the grid 10 is preferably defined by the user, the size beingthe length of the sides of the grid. The arrow 9 shown in FIG. 6 canindicate direct distances, whereas the grid 10 can indicate projecteddistances. For example the collar of an abutment must be a certaindistance below the gingival. However the gingival might not be directlyabove the collar of the abutment. By the grid 10 shown in FIG. 7 theorthographic projection from the top of the gingival between teeth tothe abutment collar represented by a control point is indicated. Anotherexample is shown in FIG. 8 where a grid is shown to indicate theorthographically projected distance between the abutment collarrepresented by a control point and the gingival ridge 12.

FIG. 9 shows an abutment model surrounded by a dental model. If the viewangle of these models was changed, e.g. by the user, the dental modelwould hide the abutment model when seen from the side. However, as shownin FIG. 10, the system and method according to the invention can providefor that part of the dental model becomes invisible when blocking theview to the abutment model.

FIG. 11 shows an abutment model displaying a grid at a control point 2′at the abutment collar and near the mouse cursor. FIG. 12 shows thecorresponding abutment model seen from above with the identical controlpoint 2′. Near said control point 2′ is no longer a grid because a gridwould be irrelevant to the customization of the abutment model when theabutment model is seen from above. Instead a curved double-arrow 13 isshown near the control point 2′. This can be seen more clearly in FIG.13, which is a close up of the control point 2′ and the arrow 13 in FIG.12. By dragging the control point 2′ the abutment model can be rotated.This rotation can be necessary to align the top ridge of the abutmentmodel with top ridges of adjacent teeth. Thus, the control point 2′ hasdifferent functionalities depending on the orientation, i.e. the viewangle for the user, of the abutment and dental models. Thereby thenecessary number of displayed control points can be reduced, i.e.simplifying the view for the user and increasing the user-friendliness.

FIG. 14 shows the same abutment model four times illustrating that acontrol point can have different functionalities independent of theorientation of the abutment model. To the left the control point at thetop of the abutment model has the functionality of increasing the heightof the abutment model. The functionality is illustrated by a symbol withan arrow pointing up. However by just a single click on the mouse thefunctionality of the top control point in the second picture from theleft has changed functionality to “tilt”, i.e. the abutment model can betilted from side to side by dragging the control point. The tiltfunctionality is illustrated by arrows pointing to each side along thetop edge of the abutment model. In the third picture from the left theabutment model has been tilted to the left and in the rightmost picturethe functionality of the control point is changed back into variation ofthe height. This shift of functionality of a control point could verywell be provided by other means, i.e. a drop down menu in the GUI or thelike. However, by the preferred method of changing the functionality bya single click with the mouse, the design process is kept quick andsimple, because the user does not have to move the mouse cursor on thescreen, but can just keep the mouse cursor on one control point.

FIG. 15 is a screenshot example from one embodiment of the systemaccording to the invention showing an abutment model surrounded by adental model and a plurality of the menus, buttons and the like, allpart of the GUI of the system. This is normal for any graphics designsystem. However, by the system and methods according to the inventionthe user-friendliness has been improved, because a plurality offeatures/tools that would normally be provided or changed by means ofbuttons and pull-down menus, in this case is automatically provided orprovided by a few clicks on a mouse button.

1. A system for designing at least one dental restoration for toothcrowns, said system having a display, and comprising: means foracquiring and displaying a three dimensional model of the dentalrestoration and/or a three dimensional dental model wherein the dentalrestoration must be fitted; means for displaying a plurality of controlpoints at the three dimensional model of the dental restoration, each ofsaid control points providing means for manually customizing the dentalrestoration model; and means for displaying an arrow at least one of thecontrol points, the length of said arrow determined by a user definedvalue, whereby the distance between the dental restoration model andneighboring objects can be measured or indicated; and/or means fordisplaying a grid at least one of the control points, the size of saidgrid determined by a user defined value, whereby the distance betweenthe dental restoration model and neighboring objects can be measured orindicated.
 2. The system according to claim 1, wherein the dentalrestoration is an implant abutment, whereby the dental restoration modelis an implant abutment model.
 3. The system according to claim 1,wherein the dental restoration is a coping, whereby the dentalrestoration model is a coping model.
 4. The system according to claim 1,wherein the dental restoration is a tooth crown, whereby the dentalrestoration model is a tooth crown model.
 5. The system according toclaim 1, wherein a control point is activated by moving the mouse cursorclose to said control point.
 6. The system according to claim 1, whereinthe arrow or a grid of a control point is only displayed when saidcontrol point is activated.
 7. The system according to claim 1, whereinthe length of an arrow or the size of a grid can be adjusted by a userwhen a control point is activated.
 8. The system according to claim 1,wherein the functionality of at least one control point is variable.9-10. (canceled)
 11. The system according to claim 1, wherein thefunctionality of at least one control point is depending on theorientation of the dental restoration model.
 12. The system according toclaim 1, wherein the view/display of at least a part of the dental modelis orientation dependent.
 13. The system according to claim 1, whereinat least a part of the dental model is invisible when said part of thedental model is between the user and the dental restoration model,whereby the dental restoration model is viewable and accessible for theuser.
 14. The system according to claim 1, wherein the control pointsare only visible when the mouse cursor is within a distance of 10 pixelsfrom the dental restoration model.
 15. The system according to claim 1,wherein at least two dental restoration models are shown simultaneouslyand wherein only the control points of the dental restoration modelclosest to the mouse cursor are visible.
 16. (canceled)
 17. A method fordesigning at least one dental restoration at a display, said methodcomprising the steps of: acquiring and displaying a three dimensionalmodel of the dental restoration and/or a three dimensional dental modelwherein the dental restoration must be fitted; displaying a plurality ofcontrol points at the three dimensional model of the dental restoration,each of said control points providing means for manually customizing thedental restoration model; and displaying an arrow at least one of thecontrol points, the length of said arrow determined by a user definedvalue, whereby the distance between the dental restoration model andneighboring objects can be measured or indicated; and/or displaying agrid at least one of the control points, the size of said griddetermined by a user defined value, whereby the distance to neighboringobjects can be indicated. 18-32. (canceled)
 33. A computer programproduct having a non-transitory computer readable medium, said computerprogram product providing a system for designing at least one dentalrestoration, said computer program product comprising means for carryingout the steps of the methods according to claim
 17. 34. The methodaccording to claim 1, wherein the display is a computer screen.
 35. Themethod according to claim 1, wherein the control points are located atthe edges of the dental restoration model.
 36. The system according toclaim 1, wherein a control point is activated by moving the mouse cursorwithin a distance of 10 pixels from the control point.
 37. The systemaccording to claim 1, wherein the length of an arrow or the size of agrid can be adjusted by a user by means of the mouse scroll wheel when acontrol point is activated.
 38. The method according to claim 17,wherein the display is a computer screen.